Cellular telephone systems are an important example of a mobile communication system. Cellular mobile telephone systems may be categorized according to those using analog modulation and those using digital modulation. One of the most widely used cellular telephone system is commonly known as the Advanced Mobile Phone System (AMPS).
An AMPS cellular telephone system typically includes a mobile telecommunication switching office (MTSO), a number of base stations (cell sites), a data link network, optional repeaters and converters, and mobile subscriber units (e.g., mobile phones). The MTSO is a special purpose switch that connects calls between mobile units and a landline telephone network. The MTSO functions to assign a voice channel to each base station. The data link network carries data between the base stations and the MTSO, and may include wired or wireless communication links. Each base station typically comprises an antenna, a controller and a number of transceivers. The controller handles the process of connecting a call between the switching system and the mobile units via a set-up channel. A mobile unit comprises a transceiver and a control unit to perform two-way communication.
These telephone systems often employ modems to transfer information between the MTSO and the transceivers. Equalization is commonly performed on a single channel. For instance, single channel equalization is often used in modems to reduce distortion on the incoming signal due to the effects of the channel. In other words, the equalizer in the modem compensates for the effects of the wire line to the signal receive location.
Other cellular telecommunication systems in use include a time-division multiple-access (TDMA) system and a code-division multiple access (CDMA) system, which are named for the type of digital modulation they employ. The European digital cellular system is known as the Global System for Mobile Communications (GSM). This system uses TDMA modulation. However, CDMA is fast becoming the standard and replacing many TDMA systems. The IS95 North American digital cellular system uses CDMA modulation.